This invention relates to ink jet apparatus having an ink jet head for ejecting droplets of ink, and more particularly, to such apparatus having a reservoir for supplying hot melt ink to the ink jet head.
The use in ink jet systems of hot melt ink, which ink is normally in a solid or frozen state but attains a liquid state or phase when its temperature is raised, has presented a number of advantages to ink jet apparatus. For a discussion of the characteristics of such ink and the use thereof in ink jet apparatus, reference is made to U.S. Pat. No. 4,390,369 and pending U.S. Applications Ser. No. 610,627, filed May 16, 1984; Ser. No. 565,124 filed Dec. 23, 1983, all assigned to the same Assignee as this invention and incorporated herein by reference.
While the use of hot melt ink has presented advantages as discussed in the above references, it also creates additional requirements for the design of the apparatus, including with respect to the reservoir system. The reservoir, which is part of the movable apparatus for devices such as ink jet printers, must be designed to maintain all of the ink in the reservoir at a substantially constant and uniform temperature so that the ink characteristics do not vary. Further, there is a need to reduce fluid flow lengths; to protect against tilting of the apparatus; and to maintain a substantially constant head of ink pressure regardless of movement of the reservoir. In order to meet these and other requirements, conventional reservoir designs as previously utilized are insufficient, and there has risen a need to a sump in the floor which provides a constant source of ink under even the most extreme tilting or transient motion conditions, the sump being located very close and to the ink jet head so as to optimize the fluid compliance seen at the manifold which feeds the ink jet array.